Two 500w heater is a bit more than needed IMO. I have the exact same size tank (240g Acrylic) and its in my basement here in Michigan. This year it's been colder than ever and my basement temps drop down into the low 60's quite often. I run a pair of 300w Jager heaters in mine and it stays at a steady 81f all the time.
I thought about 300W heaters, but with the amount the heaters are already running to keep the tank close to 80, I didn't anticipate 100W extra to be enough to keep it consistent. In a month or so, I will be running the tank at 81-82 and I honestly don't think 300W would allow me to do that.
Are you using a sump? If so, where you have your controller temp probe and/or turnover rate may effect your readings. I set my Ranco at 80F and when the probe reads 80F, the digital thermometer in the sump reads 79.2 and the digital thermometer in the internal overflow box is lower at 78.8F. The key is the ranges are fairly consistent between the 3 temp readings. Not suggesting your situation, something to consider and not all faulty equipment.
I am running a Uniquarum, so it is an internal back of tank sump with the heaters in the heater compartments on each side of the tank, the probe is in the display part of the tank. I have tested with the probe in different areas both in the tank and the filtration compartment and it is consistent each time within .2 degrees, so I know the probe location isn't what is throwing things off. I am not suggesting all faulty equipment, just that I didn't initially think the 250Ws were able to keep up with the temp based on the location of the tank and temperature in that portion of the house, etc. I am still figuring out the InkBird and do not anticipate that is faulty whatsoever.
As for the InkBird instructions, I found them to be very easy to read. They may have improved since some of you bought the unit.
The person that posted about having the InkBird set at 80 and the heaters set at 82/84, but the InkBird was only reading about 77, that is not possible the way the InkBird operates. The only way that could happen is if the heaters themselves were turning off. Even though they are set at 82/84, their setting might be off. If you turn them up then I bet you will see the tank temp come up to the InkBird setting. Also, I think it’s worth mentioning that the InkBird comes preset with a 3 degree temp differential. This means that if the temp is set at 80, the tank will cool down to 77 before the InkBird turns the heaters back on. You have to change this to 1 degree for the best use in an aquarium.
I run the InkBird 308 model with heating and cooling. I only use the heating part though.
As far as the probes go, I’ve only had one of three go bad in about a year and it didn’t fail terribly, it just went out slowly. It was only $9.99 for a new one and it replaces in seconds. If you want to wrap it or seal it somehow, then I definitely think that will help.
I still strongly recommend the InkBird as a heater controller.
This may actually still be the problem, I programmed the differential during the programming phrase and I had set it to 1 but the fact that its default was 3 and it is dropping 3 leads me to lean towards you being spot on. I am going to reset, reprogram, and see if things clean up or not.
I know the heaters aren't turning off, I have a power monitor running on the outlet and can follow the trend and see they have been pulling wattage the entire time, That was another intial thought when I first started using the controller. I started with them at 80 then kicked them up to between 82 and 84.
As previously stated, I haven't used the controller long enough to have any legitimate opinions, so to any potential buyers, don't let this be something that weighs in on your decision.
